The residency period has no bearing on what you declare as income. I moved from British Columbia to California in 1995 and the problem is, Canada taxes based on residency whereas the US taxes based on citizenship (unlike all the other countries in the world). Generally US Taxes are lower than Canada and you will get a credit for foreign taxes paid, so generally what you do is to report worldwide income and if you paid high Canadian taxes (I guarantee you did) your USA taxes for that time period will be wiped out.
